docs: def connection(self, shareable=False):
          """Get a steady, persistent DB-API 2 connection.
  
          The shareable parameter exists only for compatibility with the
          PooledDB connection method.  In reality, persistent connections
          are of course never shared with other threads.
  
          """
          try:
              con = self.thread.connection
          except AttributeError:
              con = self.steady_connection()
              if not con.threadsafety():
                  raise NotSupportedError("Database module is not thread-safe.")
              self.thread.connection = con
          con._ping_check()
          return con